This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A161145 #9 Dec 04 2017 19:02:38
%S A161145 1,7,49,77,343,539,777,2401,3773,5439,5929,7777,16807,26411,38073,
%T A161145 41503,54439,59829,77777,117649,184877,266511,290521,381073,418803,
%U A161145 456533,544439,598829,603729,777777,823543,1294139,1865577,2033647,2667511,2931621
%N A161145 Numbers which can be expressed as the product of numbers made of only sevens.
%C A161145 49 = 7 * 7; 539 = 7 * 77; 5439 = 7 * 777.
%t A161145 Module[{upto=3*10^6,sevs=Table[FromDigits[PadRight[{},n,7]],{n,7}]},Select[ Union[ Flatten[Table[Times@@@Tuples[sevs,i],{i,7}]]],#<=upto&]] (* _Harvey P. Dale_, Feb 10 2015 *)
%Y A161145 Cf. A084034, A161140, A161141, A161142, A161143, A161144, A161146, A161147.
%K A161145 nonn,base
%O A161145 1,2
%A A161145 _Claudio Meller_, Jun 03 2009
%E A161145 More terms from _Claudio Meller_, Jun 06 2009